Heat oil in a large pot on medium heat and add cumin seeds. Stir and cook for 1 minute until they just begin to darken.
Add onion and cook for 4-5 minutes til just soft, then add garlic and cook for a further minute.
Add tomatoes and carrots and stir to combine, then add ginger, coriander, turmeric, salt and pepper. Cook for 5 minutes stirring frequently.
Add water and mung beans. Increase heat to high and bring to the boil, then reduce heat, cover pot with a lid and simmer gently for 35-40 minutes until the mung beans are soft and cooked through.
Stir in chickpeas and coconut milk and bring to the boil, then turn off heat and stir in the lime juice and coriander. Taste and season with more salt and pepper as needed.